Re: Disk II Phase Question

["josephoswaldgg@hotmail.com" <josephoswald@gmail.com>]

The Disk II has a nominal rotation speed of 300 rpm; that causes one
revolution every 200 msec. The nominal read pulse spacing is 4
microseconds. That means approximately 50,000 bits in one revolution of
the disk.

Not all of these are used for data, because extra bits must be used for
the self-synchronizing bytes, in addition to allowance for "slop" when
sectors are written. Also, the standard formats must allow for the
possibility of faster drives (1% drive speed variation causes +/-500
bits in this nominal track length).

Disk recording is an analog medium. It does not easily accomodate exact
precision.